Thread tensioner



April 25, 1961 H. scHURlcH THREAD TENsIoNER Filed Sept. 13, 1957 Fig.1

INVENTOR Fig 2 States; ,Patent THREAD TENSIONER Herbert Schurich,

Karl Steinhof Germany Berlin-Frohnau, Germany, assigner toApparatefabrik, Berlin-Reinickendorf,

In hand-operated tlat knitting apparatus a thread guide is often usedwhich, as in hand knitting machines, performs the function of feeding tothe needles the thread coming from the ball or spool. In apparatus ofthis kind it is necessary to use a thread returner in the form of asprung wire arm having at its outer end an eye through which the threadpasses. The necessity for providing a thread returner of this kindarises from the reciprocating lock movement in hand-operated flatknitting apparatus since in each of the two end positions the lock hasto be moved out beyond the last needles. Since the thread guide ismounted approximately in the middle of the lock, a free thread length,corresponding to about half the length of the lock, arises between thelast needles and the thread guide. During the reversing movements of thelock this free thread length has to be brought back, since otherwisethis thread length would collect as a loop at the lock, and not onlywould this cause trouble but also the thread would at first hangcompletely slack and would not be fed to the needles, so -that nostitches could be formed. These disadvantages are avoided by means ofthe thread returner.

It was also necessary to provide between the thread guide and the threadball or spool a thread brake which gives the thread a certain tensionfor the purpose of swinging the returning bow towards the thread guide,stressing the spring of the thread returner, so that the returning bowis able, at the reversing points of the lock movement, to swing back andthereby return the thread surplus which arises.

ln practical operation it has been found that the thread brake, whichusually consists of two sprung discs lying one upon the other, has to becontinually regulated by means of an adjusting screw in order to obtainthe cor rect thread tension. This regulation depends on the thicknessand nature of the thread, and more particularly on the smoothnessthereof. This adjustment in addition to being time-wasting and difficultalso has the disadvantage that it -does not reliably ensure a uniformthread tension, and the detrimental effect of this appears moreparticularly when yarns are being used which are not uniform in naturethroughout their whole length. Particularly serious trouble arises ifthere are knops or knots in the yarn.

According to the invention all these disadvantages are avoided by thefact that a thread tensioning device is used which continuously adjustsitself automatically in dependency on the yarn thickness and the natureof the yarn. This problem is solved by the fact that the thread brake isoperatively connected with a rockably mounted sprung bow which is usednot only for returning the thread but also at the same time forregulating the braking force of the brake, the bow swinging further outwhen the thread tension increases and weakening the braking actionthrough suitable transmission means.

An embodiment of the invention chosen by way of example is particularlydescribed hereunderwith reference to the accompanying drawings, inwhich:

Figure l is a longitudinal section through a thread tensioner withspring bow;

Figure 2 shows the thread tensioner in side elevation;

Figure 3 is a front view of the thread tensioner, seen in the directionof the arrow A; and

Figure 4 is a cross section through the thread ten sioner, on line IV-IVof Figure 1.

The thread tensioner comprises a box-shaped casing 1 of which the frontwall 2 is made relatively thick and extends over` only part of theheight of the box, as is shown in Figure 1. The top and bottom edges 3of this wall are rounded and serve as support for a brake plate 4 whichhas curved lobes 5 and 6 engaging over these rounded parts and isthereby secured to the wall 2. The brake plate 4 is of upwardly taperingshape. This can be seen from the edges 7 which are inclined and convergeupwards towards one another. At the point where the vertical surface ofthe brake plate 4 merges into the upper rounded part, guide wings 8 areprovided on the two side edges 7, which wings extend vertically upwards;these wings are bent away at right angles out of the surface of thebrake plate; their shape can be seen from Figure l. These guide wingsareadapted to provide lateral guidance for the thread passing through.

The casing 1 has a rear wall 9 of which the bottom part is provided witha transverse slot 11 serving to accommodate the curved bottom end 12 ofanother brake plate 13. This second brake plate 13 is pressed againstthe iirst brake plate 12 by a twin helical spring 14. The two springcoils 15 are both mounted on one and the same pin 16 on the side walls17 and 18 of the casing. The wire ends at the two adjacent end facesofthe spring coils are combined to form a U-shaped bow 1'9. The U-shapedbow bears against the surface of the brake plate 13. The outer wire endsZtl of the spring coils bear against the rear wall 9 of the casing.

To enable the thread to be easily inserted between the brake plates, oneof the side walls, that is to say the side wall 18, is made relativelynarrow over almost the whole of its length and is offset towards theyrear wall 9, as shown in Figure 2. In its upper part only, the sidewall 18 is ywidened to form a circular disc 21. A stud 22 extends fromthe top part of the other side wall 17 and bears against the circularpart 21 of the side wall 18. The side wall 18 is connected to the stud22 by means of a screw 23. Beforehand, a helical spring part 24 of aspring bow 2S is slid on to the stud 22 from the side. The helicalspring part 24 has a downwardly extending end 26 with a hook 27 engagingin the end of the U-shaped bow'19 of the twin helical spring 14. At theend of the spring bow 25 is an eye 28 through which the thread 29passes. A forwardly open slot 31 through which the thread 29 can pass,is provided in the bottom 30 of the thread tensioner casing.

In order to guide the thread satisfactorily in the region of thetensioning discs, in addition to the presence of the Wings l3 on onetensioning plate the other tensioning plate 13 is also made slightlycurved, so as to form a channel, over the whole of its vertical portion,as is shown in Figure 4. The camber of this curved part amounts to aboutone to two tenths or a millimetre. The side edges 32 and the top edge 33of the brake plate 13 are made curved, in order to enable the thread tobe inserted easily and also to prevent sharp edges from arising, whichmight damage the thread or increase the braking action undesirably.

The manner of operation of the thread tensioner is as follows:

lf for instance the tension in the thread 29 increases as a result of aknot reaching the point of entry between the two tensioning plates, thebow 25 is moved downwards at its free end whereby the helical spring end26 is stressed and urged towards the right so that the stress due to theU-shaped bow 19 of the twin spring 14 is weakened slightly in such amanner as to loosen the brake. This causes the braking action betweenthe two brake plates to decrease, so that theV knot canV slip throughthe widening gap between the brake plates. When the knot has passed thebrake plates in this way, and the thread tension decreases again, thefree end of the bow 25 then swings upwards again accordingly so that thehelical spring end 26 relaxes again, to the left in Figure 1. Therelaxing or unstressing action onl the twin spring 14- therebydecreases, so that this spring again presses the* brake plate 13somewhat more strongly against the other brake plate 4. In this wayuniform thread tension is automatically ensured even when the thread hasgreat irregularities such as knops and knot formations. In the same way,regulation takes place when threads of difterentsurface friction anddifferent tliicknessare used. The required tension for knitting isalways produced quite automatically.

-I' claim:

1. A thread tensioner particularly for hand operated at knittingmachines, comprising aY casing, a relatively fixed brake component inthe casing, a movable brake component within the casing and cooperablewith the fixed brake component to coact with the thread passingtherebetween, spring means within the casing and in cluding a loopedportion bearing against and normally urging the movable brake componentagainst the fixed brake component, an elongated resilient bow-shapedelement having a thread guide adjacent one end of said resilient elementexteriorly of the casing, a shaft within the casing above the brakecomponents, the resilient element having a helical coil portion mountedon and turnableabout said shaft, said resilient element having a portionextending downwardly from said helical coil portion, connecting means onsaid downwardly extending portion connecting said downwardly extendingportion ofwthe resilient element with the looped portion of the springmeans so that as thread tension increases, the thread guide is displacedin a direction' toward the brake components, thereby movingvsaiddownwardly extending portion of the resilient element and looped portionof the spring means in a direction away from the movable brakecomponent, thus widening the space between the fixed and movable brakecomponents, and when the tension is relieved, the thread guide moves ina direction away from the brake components so that the downwardlyextending portion and looped portion ofthe spring means again bearsagainst the movable brake component.

2. A thread tensioner as claimed in claim l in which said spring meansincludes a pair of spaced helical coils mounted on a second shaft xed inthe casing with thc free ends of the coils bearing against the casingand said looped'portion being provided between the pair of helicalcoils, and said connecting means being defined by a hook engageable withthe looped portion of the spring means.

3. A thread tensioner' as claimed in claim l in which said movable brakecomponent comprises an elongated sheet metal member having outwardlycurved side edges and upper and lower curved ends with the curvatureextending in a direction away from the xed brake component and the lowercurved end being disposed in a transverse slotformed in the rear wall ofthe casing.

4. A thread tensioner as claimed in claim 3 wherein said sheet metalmember is concavely curved throughout the length thereof to provide achannel between thc brake components for guiding the thread.

5.'A thread tensioner as claimed in claim 1 wherein said shaft issecured in the casingy between a circular disk on one side wall and theopposite side wall of the casing.

References Cited in the file of this patent UNITED STATES PATENTSLindsay July 28, 1953

